REV. E, HILL OW THE ROCKS OF GUERNSEY. 411 
have recognized their distinctness from the rocks of the previous 
section. Those they lump together as granite, distinguishing these 
by the odd name of “ Birdseye.” 
These rocks are characterized by the predominance of hornblende. 
Sometimes the quantity is so great that hardly anything else can be 
seen. Sometimes it is segregated into large radiating prisms as 
much as an inch in length with interspaced felspar between. (This 
is in patches, called by the workmen ‘‘Sunburned,”’ and appears to 
be connected with veins, or possibly with dykes.) More often it has 
formed itself into huge skeleton crystals crowded with felspar in- 
clusions, but showing their unity by the lustre of their cleavage- 
faces. These reach an enormous size, one face sometimes occupying 
two square inches of a specimen. The felspar is generally in 
irregular grains, similar to saussurite, while in the diorites and 
syenites it is often in well-shaped crystals. At Mont Crevelt it has 
a pale greenish tint. Although the normal rock is so distinct from 
the diorites, yet it is by no means always easy to say whether an 
outcrop belongs to one group or another. 
The north and south limits on the shore are well marked, the 
transition being very abrupt. At Hougue 4 la Perre Battery the 
hornblende aggregates give the boulders smoothed by the sea 
a peculiar spotted appearance, which is very striking and quite 
different from the uniform surface on the other outcrop a few yards 
to the south. This spotted appearance is seen at some other points, 
but nowhere more strikingly than here. 
These rocks, like those of the previous section, present several 
varieties, which may possibly be of several ages. The very large 
skeleton hornblende crystals are seen at Hougue a la Perre, the quarry 
on the Grande Maison Road, and that on Baubigny Hill; the rock 
of the Bouet and of the Delancy Hill quarry has its hornblende in 
smaller crystals irregularly felted together, with a small proportion 
of felspar ; the rock north of St. Sampson’s Harbour has more felspar 
still, and does not very closely resemble the above, though it differs 
widely from the diorites which are close to it. All the rocks of 
Guernsey are cut by dykes, but these far beyond the rest, and as 
many of these dykes are hornblendic it occasionally becomes difficult 
to say what is normal rock, and what mere local intrusion. Thus 
a singular black rock on the north shore of Bellegreve Bay, with a 
strong jointing that approaches a cleavage, may possibly be a form 
of the intrusive rock which the quarrymen designate ‘“‘ Long grain.” 
I believe, however, it is only a form of the normal “ Birdseye.” So 
again on the shore by Mont Crevelt, where the south pier of St. 
Sampson’s Harbour runs out into the sea, there are appearances 
which may be due to a fault-breccia, but may also be due to a 
shattering by intrusions. I feel sure that among these numerous 
intrusive dykes many belong to the group of the previous section, 
so that these rocks must be older, although their position as an oval 
mass in the midst of those others would rather suggest a posterior 
date. 
The question whether these rocks are metamorphic or igneous 
jam SSS 
